DocID018532 Rev 3

7/13

PM0083

Software interface

2.4

Programming mode entry

When the STM8T143 boots up after power-on, it checks for a programming mode entry

sequence on POUT. If the programming mode entry sequence is recognized on POUT, it

enters programming mode. If the programming mode entry sequence is not recognized,

then it will enter functional mode.

Table 5. Programming mode entry procedure

Step

Action

Description

1.

Set up I/Os

CX output (Data), POUT output (Clock).

2.

All outputs = LOW

Prevent device from being powered through any of the I/Os.

3.

Wait 200 ms

Wait for all capacitors to discharge after previous test (if any).

4.

Device power ON

VDD = 5 V

5.

Change CX to an input

Configure CX as input on the programming tool so that STM8T143

can take control of CX.

6.

Wait for at least 4 ms but

not more than 7 ms

Wait for device to start boot sequence and VREG to stabilize.

7.

POUT - clock 8 pulses.

See Figure 2.

The timing on POUT is important. This timing is taken from the

center frequency of the STM8T143. If the frequency is changed, or

not according to specification (for example due to tampering with

tuning options), then the timing needs to be scaled accordingly.

8.

POUT = HIGH

Pull POUT high to indicate to the device that the programming tool

is ready to send data.

9.

Wait 560 µs

Wait for the device to respond.

10. Wait for CX = HIGH

Check if the STM8T143 has pulled CX high. If CX is not high, then

it did not enter programming mode. If CX is high then there is a

good probability that it entered programming mode.

11. Write 0xF0

Write the 0xF0 command to request an acknowledge.

12. Read

Read the reply byte.

13. Check if reply = 0xA5

If the result is 0xA5 then confirmation has been received from the

device that it is actually in programming mode.